Aneurysms occur in blood vessels at sites where, due to age, disease or genetic predisposition, the strength or resilience of the vessel wall is insufficient to prevent ballooning or stretching of the wall as blood flows therethrough. If the aneurysm is left untreated, the blood vessel wall may expand to a point at which rupture occurs, often leading to death.
To prevent rupturing of an aneurysm, such as an abdominal aortic aneurysm, a stent graft may be introduced into a blood vessel percutaneously and deployed to span the aneurysmal sac. The outer surface of each end of the stent graft is preferably sealed against the interior wall of the blood vessel at a site where the interior wall has not suffered a loss of strength or resilience. Blood flowing through the vessel is channeled through the hollow interior of the stent graft to reduce, if not eliminate, the stress on the vessel wall at the location of the aneurysmal sac. Therefore, the risk of rupture of the blood vessel wall at the aneurysmal location is significantly reduced or eliminated, and blood can pass through the vessel without interruption.
Stent grafts include a graft fabric secured to a stent. The graft is typically inserted into or pulled over the stent and sewn to its structural components. Alternatively, the stent may be formed on the graft such that the individual wires of the stent are threaded through specially provided projecting fabric loops on the surface of the graft. The stent provides rigidity and structure to hold the graft open in a tubular configuration as well as the outward radial force needed to create a seal between the graft and the vessel wall. The graft provides the tubular channel for blood flow past the aneurysm and prevents blood from pressurizing the aneurysmal sac.